On an ideal day for low scoring at the TPC Sawgrass where the par-72 Stadium Course has been softened by recent rain, Germany's Kaymer raced home in a sizzling seven-under-par 29 to complete a nine-under 63.
His back nine, holes one to nine, set a new low for the tournament while his 63 matched the record scores previously posted at the Players Championship by Fred Couples (1992), Greg Norman (1994) and Roberto Castro (2013).
"I didn't make many mistakes today, which was nice," Kaymer told reporters after a flawless nine-birdie display in the PGA Tour's flagship event which is widely regarded as the unofficial fifth major.
"I missed only one fairway, which was on 16. So overall my ball-striking was very good. Fortunately I could take advantage of some putts on my back nine, on the front, on the golf course. It was just a very, very good round of golf."
Kaymer sank a 16-footer at the par-three eighth, then got up and down from a greenside bunker at the par-five ninth to end the day two strokes in front of American Russell Henley, who had set the clubhouse lead with a sparkling 65 in the morning.
South Korea's Bae Sang-moon opened with a 66 while U.S. Open champion Justin Rose, England's former world number one Lee Westwood and 2008 Players champion Sergio Garcia of Spain were among a large group on 67.
Northern Ireland's Rory McIlroy got to five under after 11 holes on a hot and sunny morning at the TPC Sawgrass but then struggled coming home on the way to an opening 70.
"I played well pretty much the whole way around, I just let a couple of shots get away from me at the end," McIlroy said.
"So I'll come out tomorrow and try and attack again, because I feel like you can go low on this golf course this week. It's soft, the greens are receptive."
Former world number one Kaymer, who landed his only major title at the 2010 PGA Championship, birdied the 11th and 15th to reach the turn in two-under 34.
He continued to build momentum, picking up further shots at the first, second, fourth, sixth, seventh, eighth and ninth to shoot the first ever 29 over nine holes at the TPC Sawgrass.
"If you strike it very well, you gain confidence hole after hole, and then you feel like you can become maybe a little bit more aggressive," said the 29-year-old German, a 10-times winner on the European Tour.
"It's nice to make some history. No one shot 29 on that golf course before and I did it today. But it's only the first round of a long, long tournament."
Henley, a double winner on the PGA Tour who is known for his streaky putting, piled up six birdies after the turn to set the early pace at the TPC Sawgrass.
"I got off to a good start and I felt really comfortable on the greens today," said the 25-year-old from Georgia after mixing nine birdies with a double-bogey at the par-four seventh.
"As long as I keep feeling comfortable with the putter, I think I can putt well on these greens. Hopefully, I can do that for the next three days."
British Open champion Phil Mickelson struggled to an opening 75 while Australian world number two Adam Scott, who could take over the top spot from the absent Tiger Woods after this week's event, fared even worse with a 77.
With last year's winner Woods sidelined since having surgery for a pinched nerve in his back at the end of March, Scott needs to finish no worse than joint 16th this week to become number one for the first time.
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